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Subject: Re: [PATCH v4] net: ravb: Fix possible UAF bug in ravb_remove
To:     Paolo Abeni <pabeni@redhat.com>, Jakub Kicinski <kuba@kernel.org>,
        Zheng Wang <zyytlz.wz@163.com>
CC:     <lee@kernel.org>, <linyunsheng@huawei.com>, <davem@davemloft.net>,
        <edumazet@google.com>, <richardcochran@gmail.com>,
        <p.zabel@pengutronix.de>, <geert+renesas@glider.be>,
        <magnus.damm@gmail.com>, <yoshihiro.shimoda.uh@renesas.com>,
        <biju.das.jz@bp.renesas.com>, <wsa+renesas@sang-engineering.com>,
        <netdev@vger.kernel.org>, <linux-renesas-soc@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <hackerzheng666@gmail.com>,
        <1395428693sheep@gmail.com>, <alex000young@gmail.com>
References: <20230725030026.1664873-1-zyytlz.wz@163.com>
 <20230725201952.2f23bb3b@kernel.org>
 <9cfa70cca3cb1dd20bb2cab70a213e5a4dd28f89.camel@redhat.com>
From:   Sergey Shtylyov <s.shtylyov@omp.ru>
Organization: Open Mobile Platform
Message-ID: <607f4fe4-5a59-39dd-71c2-0cf769b48187@omp.ru>
Date:   Thu, 27 Jul 2023 21:48:41 +0300
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Hello!

On 7/27/23 11:21 AM, Paolo Abeni wrote:
[...]
>>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>>> index 4d6b3b7d6abb..ce2da5101e51 100644
>>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>>> @@ -2885,6 +2885,9 @@ static int ravb_remove(struct platform_device *pdev)
>>>  	struct ravb_private *priv = netdev_priv(ndev);
>>>  	const struct ravb_hw_info *info = priv->info;
>>>  
>>> +	netif_carrier_off(ndev);
>>> +	netif_tx_disable(ndev);
>>> +	cancel_work_sync(&priv->work);
>>
>> Still racy, the carrier can come back up after canceling the work.
> 
> I must admit I don't see how/when this driver sets the carrier on ?!?

   The phylib code does it for this MAC driver, see the call tree of
phy_link_change(), on e.g. https://elixir.bootlin.com/linux/v6.5-rc3/source/...

>> But whatever, this is a non-issue in the first place.
> 
> Do you mean the UaF can't happen? I think that is real. 

   Looks possible to me, at least now... and anyway, shouldn't we clean up
after ourselves if we call schedule_work()?However my current impression is
that cancel_work_sync() should be called from ravb_close(), after calling
phy_{stop|disconnect}()...

>> The fact that ravb_tx_timeout_work doesn't take any locks seems much
>> more suspicious.
> 
> Indeed! But that should be a different patch, right?

   Yes.

> Waiting a little more for feedback from renesas.

   Renesas historically hasn't shown much interest to reviewing the sh_eth/ravb
driver patches, so I took that task upon myself. I also happen to be a nominal
author of this driver... :-)

> /P

MBR, Sergey